How is the process of development controlled? What is the circuitry involved in the cell's decision to simply divide or to begin the process of differentiation? We have isolated and characterized several Bacillus subtilis genes which are involved in the transition from vegetative growth to the developmental mode which results in the appearance of dormant endospores. These genes show complex patterns of regulation, both at the level of transcription (alternative RNA polymerases) and translation, and one of the aims of the proposal is to study the nature of the regulatory mechanisms, i.e., promoter structure, cis and trans- acting factors involved in gene activation, in vitro transcription, etc. We postulate that many of the proteins encoded by early sporulation genes, of the spoO class, encode proteins which function during vegetative growth as well as at the beginning of the differentiation process, and that these proteins form a functional complex at some point during the growth cycle. Homology between two of the early spoO proteins, spoOA and spoOF, and a series of regulatory proteins involved in the sensing of environmental signals in other bacteria, suggests model for the control of sporulation. Another of the aims of this proposal is to purify spoO proteins and to provide evidence for the model. One of the genes we have isolated, the sin ORF2 seems to code for a repressor of certain late growth functions, i.e., sporulation and exprotease synthesis, but is a positive regulator for competence genes. Our last aim is to study the sin gene product and its role in the regulation of differentiation.